Plant growth is heavily influenced by the surrounding environmental climatic variables and by the amount of water and fertilizers supplied by irrigation. This is a main reason why a greenhouse is ideal for cultivation, since it constitutes a closed environment in which climatic and fertirrigation variables can be controlled to allow an optimal growth and development of the crop.
Among the climatic conditions are temperature, relative humidity (RH) and CO2 concentration. For optimal growing of many plants, temperature in a growing system (e.g., a greenhouse or other indoor growing environment) should be controllable between 55° F. and 80° F. in the growing space. CO2 concentration in the greenhouse should be controllable between atmospheric levels of 400 ppm and 1,500 ppm. And relative humidity in the space should controllable between 35% RH and 80% RH. Water condensation and recovery from plant transpiration, for healthy plants, will be between 0.2 liters/plant/day and 3 liters/plant/day, depending upon the plant and conditions.
Known greenhouse systems address some of these variables, individually. Some greenhouse systems have been devised to enrich the air with CO2. Others have been devised to heat air when ambient conditions are cold. Others cool air when ambient conditions are hot. If the source of CO2 is natural gas engine or boiler exhaust, it becomes difficult to prevent increases in temperature and water vapor beyond those suitable for plants. High temperature exhaust contains appreciable water vapor as a byproduct of combustion. None of the prior art systems combines heating and cooling to control temperature and relative humidity of a CO2 enriched stream of air while capturing condensate, particular where the source of CO2 is exhaust from a natural gas engine or boiler.
Fungus and bacteria are influenced by humidity and temperature. High humidity inside greenhouses, at least at certain periods of time, favors the formation of fungal spores, accelerating their development, as well as the growth of bacterial colonies, especially if temperatures are favorable. These risks become higher when water vapor condenses on the plants. During daytime, RH decreases in the greenhouse when temperature increases, although the absolute humidity increases due to transpiration. At night, as the greenhouse gets colder, the RH increases and may reach saturation, at which point condensation occurs. Such conditions are ideal for mold and bacteria formation and growth, each of which compromises the health of the plants.
A greenhouse climate management system that allows for simultaneously maintaining a set of climate factors (temperature, humidity, CO2) close to pre-established set point values, respecting certain rules established by a user, is needed. What is needed is a year-round system and method of maintaining the temperature and relative humidity of a CO2 enriched stream of air within acceptable ranges for optimal plant growth in a greenhouse, while capturing appreciable condensate. The system should preferably be efficient, reliable, scalable and adaptable to existing greenhouses. The system should work with CO2 enrichment from exhaust from an engine or boiler that consumes natural gas.
The invention is directed to overcoming one or more of the problems and solving one or more of the needs as set forth above.